Copper is a metal widely distributed in nature. The efficacy of the antimicrobial activity of products based in copper has motivated the development of different studies aimed to know the mechanisms involved in this activity, as well as evaluating potential industrial applications for this metal.
Phyllis J Khun, a bacteriologist, demonstrated in 1983 the antimicrobial properties of copper. In 2008, the US Environmental Protection Agency (EPA) published a bibliographical review on the different properties of copper and its benefits in human health, among which its bacteriostatic, fungistatic bactericide, fungicide, and sanitation and disinfection powers are emphasized.
The effectiveness of products based in copper as antimicrobial agents has motivated scientists to design new applications in the health area.
The mechanism associated with the antibacterial activity of copper is still uncertain. Some studies suggests that copper in high concentrations can have a toxic effect on bacteria due to its tendency to alter between its different oxidation states, the generation of hydroxyl radicals, highly reactive, and being able to damage essential bacterial biomolecules. These radicals could act by substitution of essential ions conducting to interference in: protein synthesis; enzymatic activity or functions of the bacterial cell membrane. On the contrary, toxicity of host cells caused by DNA damage seems unlikely. In fact, there are observations suggesting that copper can protect host cells from DNA damage caused by hydrogen peroxide.
The molds for earpieces, such as earplugs for aquatic sports or those related to acustic trauma, audio devices and earphones in general (for example retro-auricular earpieces, intracanal earphones and completely in canal (CIC) earphones), are essential part of the devices, since the mold is the one which is adjusted to the ear of the user. For example, in the case of hypoacusia, it is required that earpiece molds are custom fabricated considering each user. Also, these earpieces allow acoustic sealing of the ear canal and acoustic modification of the aural signal. When fabricating the molds, the following aspects must be considered: comfort degree, aesthetical appeal, operative easiness, and patient tolerance to the materials. Different variations can be made to the earpiece mold in order to produce a lighter, more comfortable and more suitable earpiece depending on its application. Even molds containing inside an aural device can be fabricated. Nevertheless, sometimes users of earpieces have allergic reactions to the material of a particular mold and the mold must be replaced by a different material.
Otitis externa has been described as one of the complications associated to the prolonged use of earpiece devices, and particularly to the use of earphones and earplugs, since in order to avoid the feedback effect, the earpiece mold must completely seal the ear canal, which contributes to the development of a series of additional problems such as lack of air circulation, perturbation in earwax evacuation and facilitation of protective earwax being dissolved by humidity, thus making the skin of the ear canal more susceptible of infections caused by bacteria or fungus. Therefore, patients with hypoacusia are earphone users and develop otitis externa, whom while being in treatment for the infection must stop the use of the earphone, which results in deterioration of their sensorial capacity and their quality of life.
A solution to the previously mentioned problems is described in the document US 2004/0161445, which describes an earphone or an earphone component to be positioned in the ear canal, which comprises a biofilm inhibitory coating. The coating comprises an inorganic condensate modified by some organic groups on the base of coating compositions, including a hydrolyzed or a pre condensed of one or more compounds which can be hydrolyzed with at least one substituent which cannot be hydrolyzed, wherein at least one portion of the organic groups of the condensate include fluorine atoms and/or silver or copper colloids contained in the coating.
A similar solution is described in document US 2004/0179709, which describes at least one membrane of a miniature transducer comprising, at least in part, an hydrophobic and or oleophobic and or biofilm inhibitor coating, which due to the thickness of the coating is less than 10 μm, thus it does not affects significantly the auditory features of the transducer, and prevents the degradation of the transmission features due to humidity, or damages caused by humidity of the transducer. Additionally, the coating can contain copper or silver colloids, and preferentially comprises silver ion colloids.
Although the previously cited documents describe the use of copper ions to inhibit the formation of a biofilm in earphones, it is clearly seen that both documents disclose coatings made from compounds which can have copper ions in its compositions. Nevertheless, using copper ions in the coating composition carries different drawbacks, such as:                In the first place, copper ions cannot be separated, which are the ones exerting the antimicrobial activity, to mix them with the polymer in the mold, and thus, they have to be released in a solution to allow them to exert their action mainly to bacterial membranes. Cu2+ ion, being free or bonded to the polymer, will not be able to free itself from the polymer since if the bond is covalent, it will be extremely difficult to free and exert its antibacterial action.        In second place, EPA, which is the organization certifying the antimicrobial copper properties, only approved metallic copper as having the specific features described in the present application, therefore the effectiveness of ionic copper is not proved.        In third place, using copper ions present in coatings can produce harmful effects to the user's skin, by being the coating in direct contact with the skin, which can produce contact dermatitis and green coloring of the skin.        
In consequence, it can be seen that using ionic copper in compounds destined for earphone mold coatings does not allow preventing in an sufficiently effective manner the formation of a biofilm, and thus, it neither does prevent effectively the presence of infections; which could generate further possible adverse effects on the users, produced by the direct contact of the copper and skin.
In this way, there is a need in the field of the invention to provide a mold for earpiece devices allowing to prevent, in an effective manner, potential infections, producing a positive effect in preventing otitis externa in users and allowing at the same time, avoiding direct contact of the metal with the skin, in order to avoid adverse effects to the user.
In order to overcome the problems described, a mechanism is presented in which the copper exerts its antimicrobial properties in earpiece devices comprising a metallic piece with biocide properties, preferentially made of copper, allowing to prevent in an effective way potential infections, producing a positive effect in preventing otitis externa in the user. These earpiece devices can be adjusted to the shape of the ear canal or to the ear shell, and the metallic piece is located inside, avoiding direct contact between the metallic piece and the skin. The metallic piece can be a plate and/or similar which is adjusted, from inside the mold, to the shape of the external contour of the same, covering all the zones wherein the surface of the mold is in direct contact with the skin, allowing at the same time that only said mold is in direct contact with the skin of the user.
In this way, the described earpiece device allows solving in an effective manner the deficiencies described in the state of the art by providing earpiece devices comprising a metallic piece inside, avoiding direct contact between said metallic piece and the skin, allowing at the same time the adherence of pathogenic strains to the surface of the mold, of bacteria as well as fungus, thanks to the properties that said metallic piece provides, avoiding potential infections, and producing a positive effect in preventing otitis externa in a user.